TXX-9335, Forwards Omega Point Lab Test Repts for Most Recent Util Fire Endurance Tests.Engineering Rept ER-EE-006,Rev 0, Evaluation of Fire Endurance Test Results Related to Cable Functionality in 1-1/2 & 2 Inch Conduits Also Encl

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Forwards Omega Point Lab Test Repts for Most Recent Util Fire Endurance Tests.Engineering Rept ER-EE-006,Rev 0, Evaluation of Fire Endurance Test Results Related to Cable Functionality in 1-1/2 & 2 Inch Conduits Also Encl
ML20059F492
Person / Time
Site: Comanche Peak Luminant icon.png
Issue date: 10/28/1993
From: William Cahill
TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20059F495 List:
References
TXX-93353, NUDOCS 9311040328
Download: ML20059F492 (10)
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h, j Log il TXX-93353 r r File # 10010 9U9'5 TUELECTRIC October 28, 1993 WHliam J. Cahill, Jr.

Group %cr President U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 P

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) - UNIT 1 DOCKET NO. 50-445 THERMO-LAG LABORATORY TEST RESULTS AND RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION FOR CPSES UNIT 1 REF: 1. TU Electric letter logged TXX-93254 from William J. Cahill, Jr., to NRC ddted July 13, 1993

2. NRC letter dated October 29, 1992, from Suzanne C. Black to William J. Cahill, Jr.

Gentlemen:

TU Electric is providing via Enclosures 1 through 5 copies of the laboratory test reports for the most recent TU Electric fire endurance tests. These test reports are listed in Attachment (1). The testing documented in these reports (for Unit 1) was conducted under the auspices of Omega Point Laboratories at San Antonio, Texas, in a manner similar to the Unit 2 tests.

Also enclosed as Enclosure 6 is an engineering report on cable functionality for 1-1/2 incn and 2 inch non-upgraded conduits using the temperature profiles obtained from the existing CPSES fire test results of non-upgraded conduits.

During a meeting on September 20, 1993, your staff raised some questions regarding the effects of a 90 degree C cnnductor temperature on operability of fire tested cables, arid the effects of elevated temperatures on plant cables with respect to c:able aging. TU Electric's responses are provided in Attcchment 2 for information only.

These items are not mcorporated into the TU Electric thermo-lag barrier documeatation as these issues are not part of the acceptance criteria by the NRC ir, reference 1.

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hlhf 9311040328 931028  % /

PDR ADOCK 05000445 6 40 N. Olive Street LB. 81 Dalin,Texn 75201 F pm y

l TXX-93353  !

.-- Page 2 of 2 i Please contact Obaid Bhatty at (817) 897-5839 should you require additional l information. ,

J Sincerely, j 1

8 .) ,.

William J. Cahill, Jr.  ;

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Ahf cwg 1.

By: Roger D. Walker i Manager of Regu'atory Affairs ,

i OB:tg i Attachments Enclosures  !

cc w/o enclosures:  ;

Mr. J. L. Milhoan, Region IV l Mr. L. A. Yandell, Region IV Mr. T. A. Bergman, NRR t Mr. S. K. West, NRR Resident inspectors ,

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ATTACHMENT 1 TO TXX-93353

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Attachment 1 to TXX-93353  :

Page 1 of 1 LIST OF TEST REPORTS NQ. SCHEME # CONFIGURATION

1) 11-5 (3) 24"X4" CABLE TRAYS WITH DIFFERENT JOINT j REINFORCEMENT TECHNIQUES j
2) 13-2 12"X4" CABLE TRAY (NON-UPGRADE) 2" DIA. CONDUIT (UPGRADE AT RADIAL BENDS ONLY)
3) 11-2 24"X4" CABLE TRAY.WITH 1-1/2" AND 2" DIA. CABLE l AIR DROP BUNDLES  !
4) 11-4 (2) 24"X4" TRAYS (STACKED) WITH CABLE AIR DROPS  !'

THROUGH EMBEDDED SLEEVES COVERED BY A " BOX" CONFIGURATION

5) 15-2 36"X4" EXPOSED CABLE TRAY WITH (2) INDIVIDUALLY {

WRAPPED 750 MCM CABLES  ;

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ATTACHMENT 2 TO TXX-93353  !

ANSWERS TO NRC QUESTIONS FROM THE MEETING OF SEPTEMBER 20, 1993 RE: EFFECTS OF 90 DEGREE C CONDUCTOR TEMPERATURE AND CABLE AGING r

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_.. . .- ~. - - .

10/23/93 This evaluation addresses two questions raised by the NRC. The first dealt with the effects of a 90 degree C conductor temperature on operability of fire tested cables, and the second; the effects of '

elevated temperatures on plant cables, with respect to cable aging. Both issues, to one degree or another, were evaluated in light of Comanche Peak Steam Electric Station (CPSES) Qualification documents. All Class-1E cables have been qualified for 40 years with the cable operating at a  ;

conductor temperature of 90 degrees C. As an example a Cross-link Polyethylene (XLPE) insulated i

Firewall 111 cable was aged at a temperature of 150 degrees C for a period of 941 hours0.0109 days <br />0.261 hours <br />0.00156 weeks <br />3.580505e-4 months <br /> (this is equivalent to more than 45 years of qualified life). Following the thermal aging the cable was exposed to irradiation and a simulated Loss of Coolant Accident (LOCA).The cables were then subjected to an 80v/ mil voltage withstand test for 5 minutes. This amount of voltage stress is equivalent to 80 percent of the factory testing, which was performed at 100 v/ mil. This level of testing is sufficent to demonstrate that the physical and chemical properties of the cable had not been adversely affected by the thermal aging, irradiation aging, or the simulated LOCA tests. The following calculation is i based on characteristics associated with Firewall !!1 cable.  ;

The first question we will address will be the effect that the fire test would have on a cable operating at rated current and voltage (i.e. 90 degree C conductor temperature, based on 50 degree C ambient  :

and a 40 degree C conductor temperature rise). We will demonstrate analytically that the leakage ,

currents associated with cables operating at 90 degrees C, prior to a fire, are insignificant. If the I cables had been operating at rated current and voltage during the fire test, the cables could be j assumed to be operating at 40 degrees C above ambient. Since there is no stabilized ambient during a fire test, the most accurate approximation would be the average temperature of the cable jacket.

This is a conservative analysis method because of the u.ermal tag between the outerjacket and the conductor. Copper is also an excellent thermal conductor and will act as a temperature averager and thus prevent localized insulation hot spots. The highest temperatures associated with a thermolag ,

configuration, which will be utilized at CPSES, were seen in scheme 9-3 and were associated with l the 1 1/2 and the 2 inch conduits. Toe maximum average temperature associated with the cable jacket ( which we will utilize as the ambient temperture) was 296 degrees F. To determine the conductor temperature we will add 4G degrees C (104 deg F) to the ambient temperature. This will l give us a maximum conductor and insu,3 tion temperature of 400 degrees F. Utilizing the analysis I method contained in ER-EE-006 (see erciosure 6) we have the following:

For the worst case with the current @ 4ma 5 M c b" F '400 D = .118 d :.058 1. = 20 t -(F - 32) + 273 K = 1.65810 9 , jo 6 0

E3': 40 R in 250 1 j a.004 1 2*l 1 IR"' x IR K log - IR' =

E E 3

R t- -R in E A4 : R t= 9.7510 1R' : lR' 10' EA4 = 39 I 1 R in R in\

- + -- + 1 gRt E~ ,

6 R j = 1.2310 I I 3 = 3 91210'  % Error 4ma = 4 00 3 " IR 4 10 3

%Enor 4ma = 0 098 l

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10/23/93 i

Where:

F = Temperature of insulation in degrees F. l D = Diameter over the insulation in inches.

d = Diameter over the conductor in inches.

L = Length of cable exposed to elevated temperatures. '

t = Temperature of insulation in degrees K. i K = Insulation Resistance constant. i E3 = Loop power supply.

R in = NLP card input resistance. ,

1; = Loop power supply current. >

I2 = Transmitter current.  ;

1 3 = Leakage current. [

IR = Insulation resistance in Meg ohms - 1000 ft.

I IR' = Insulation resistance for a cable length,in Meg ohms and ft. l IR" = Insulation resistance for a cable length,in ohms and ft. f f

IR* = Insulation resistance for a ideal cable with zero leakage current.

Rt = Transmitter resistance.

l R; = Cable insulation resistance.  ;

EA4 = Voltage actoss transmitter at 4 ma.

Therefore; the leakage currents associated with this temperature would be insignificant for this worst case ambient temperature configuration.  !

l The second question raised by the NRC dealt with cable aging; specificly, would the elevated l temperatures associated with the fire tests have any adverse affect on an aged cable. We will  !

demonstrate anaalytically that these elevated temperatures from the fire have no adverse effect on cable operation during the fire even if the cable were previously aged. Below is an evaluation, utilizing 4 the Arrhenius method, to determine these affects. Since the affects of thermal aging are additive we will utilize the last 11 minutes when the maximum cable jacket temperatures exceeded 386 degrees F. For each minute the maximum temperatures will be utilized. This is conservative since the maximum temperatures occur in the final seconds of the evaluation period, but for evaluation purposes the maximum temperature is being utilized for the entire time period. The following calculation shows that the cable ages approximately 3 years during this time period. Aging the i cable at 150 degrees C for a period of 941 hours0.0109 days <br />0.261 hours <br />0.00156 weeks <br />3.580505e-4 months <br /> is equivalent to a qualified life of more than 45 years.

l Even based on this worst case there is sufficient margin to ensure cable operablity. This evaluatulon l will also demonstrate that, based on actual cable parameters, the amount of additional aging will not

] adversely affect a cable's performance and is bounded by our LOCA test qualification. The calculation j is as follows:

4 t 2 = 0.0167 Ea .= 1.34 K = 8.61710 T j = 90 4 273 1 i page 2 of 5

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10/23/93 i:

Where:

12 = actual exposure (hours) at T 2

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T 3 = service temperature (deg K) '

E , = activation energy (eV) .

K = Boltzmann's constant = 8.617E-S f i

t 2 represents the actual exposure time at the elevated temperatures and will be calculated at j eleven different points utilizing a matrix.

T 3 is the service temperature of the insulation and corrosponds to the temperature of the conductor, it has been converted from degrees C to degrees K.

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.' 393 '

401 409 j

'417  !

425 - -

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F2 434 T2 4

g(F2 - 32 + 273 442 1 451 l 459 I 469  !

478  !

i VA ere:  % i tj = equivalent aging (hours) at T 3  ;

T2 = actual exposure temperature (deg K)

F2 = actual exposure temperature (deg F)

F2 represents the last 11 temperatures of the fire test, and each temperature will be evaluated for a period of one minute.

T2 converts the temperatures contained within the matrix to degrees K.

tj is the equation to determine the equivalent aging associated wrth the elevated temperatures.

This equation has been vectorized in order to accommodate the temperature matrix.

page 3 of 5

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10/23/93  ;

.i The equivalent aging in hours is provided in the following matrir: l i

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, 368.28  :

I 499.782  !

674.435 905.156 3

1.208 10 t I 3 1.662 10  !

3

, 2.195 10 .l 3

2.984 10 3

3.9 10 l 3

5.415 10 3

7.234 10 t

in order to provide this information in a more useful format the data will be converted to years. l 0.042  !

t 0.057 l 0.077 i 0.103 f 1; 0.138 t

f t )7, = 0.19

.Q 373 l 0.251  !

t 0.341

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0.445 i f

0618 i

[0.826 i

The equivalent total aging is the sum of the data contained within the matrix: f i

.042 + .057 + .077 + _103 + .138 + .19 + .2514 .341 + .445 + 618 + 826 = 3.088 I I

I Utilizing the same methodology an analysis was performed which evaluated the entire 60 minute time -!

period. The results demonstrated that the total aging associated with the test would have been 3.2  !

years. This amount of additional aging is insignificant and will not have any impact on the results of I this evaluation.  ?

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10/23/93  ;

The insulation temperature utilized within the Arrhenius equations for the qualification of electrical t power cable assumes an insulation temperature of 90 degrees C.This is an extremely conservative  !

methodology, typically cables at CPSES are designed with sufficient ampacity margin to prevent the  ;

conductor temperature from exceeding 75 degrees C. Allowing for a conductor / insulation temperature  ;

of 75 degrees C yields an expected cable life of 253 years. The calculation for this evaluation is I contained on the following page:

t

] t 2 2220730 Ea .: 1.34 K = 8.617104 -

+ 273 T 3 = 90 273 F2 =167 T2= F2 - 32)

'r.d / i 1' t  !

j T2 - 273 = 75 t j rt 2e JI(Fi T 2" )' t t I t g = 40 t3 4rs ' 24 365 g

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t 2 Ts = 253.508 '

] 3 1

i Where: ,

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t tj = Equivalent aging (hours) at T j ~

i t 2 = Actuaul exposure (hours) at T, l T j = Service temperature (deg K).

T2 = Actual exposure temperature (deg K).

F2 = Actual exposure temperature (deg F). >

E, = Activation energy.

1 m = riquivalent aging in years. l

< 3.rs= Actual exposure in years.

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2 Since Arrhenius and aging effects are cumulative it is acceptable to subtract the amount of aging due to exposure to the fire temperature from the expected life. This will yield and expected life wellin excess of the required 40 year operating life of CPSES.

CONCLUSION:

4 The foregoing analysis demostrates that the answer to either question is that the cable would perform ris intended fuction. Neither the effects of operating the cable at rated current and voltage during the fire test nor the effects due to cable aging, would adversely impact the cable performance.

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